Needle assemblies provided with a piercing element are used in a wide variety of contexts to administer medication and withdraw fluids. These needle assemblies include, by way of example, hypodermic needles, catheter needles and blood collecting needles. It is recognized in the medical community that it is preferable to utilize a needle assembly which is safe and readily easy to use.
In the past, to provide a measure of safety, needle assemblies have included a rigid cylindrical cap positioned over the cannula and engaging the device to which the cannula is connected. During use, the cylindrical cap is removed to expose the cannula. After using the needle assembly for its intended purpose, the cylindrical cap must be once again mounted on the hub to cover the used cannula. Oftentimes, the healthcare professional tries to reposition the cylindrical cap on the needle assembly by “scooping” the cylindrical cap with the needle assembly. As can be appreciated, this may not be an easy or effective technique for repositioning the protective cap on the needle assembly. Also, the cap may become accidentally dislodged from the needle assembly, thus exposing the used cannula and presenting a potential danger.
Other proposals have also been made to incorporate safety attributes into needle assemblies. These proposals are generally divided into three categories: 1) hinged recap devices in which a hinged sleeve is pivoted into a permanently locked position with respect to the cannula; 2) retractable cannula devices in which the cannula is retracted into the syringe barrel or the syringe plunger; and 3) sliding barrel devices in which the syringe barrel is formed by two concentric cylinders, the outer one of which is slid by the health care worker towards the cannula after use to cover the cannula. Although these assemblies provide some additional measure of safety, difficulties remain.
For example, hinged recap devices may be assembled between the syringe and needle assembly. This construction introduces dead space between the cannula and the syringe, thereby resulting in the waste of expensive medication. Retractable cannula devices run the risk of inadvertently retracting, thus wasting a syringe and once again presenting the possibility of wasting expensive medication. Additionally, the velocity of the cannula retraction could result in the spraying or splashing of fluids or medication, thus actually increasing the healthcare professional's exposure risk. The sliding barrel design is disadvantageous in that it almost doubles the length of the syringe from the unused position to the used/disabled/engaged position, thus substantially increasing the volume of biohazard waste and possibly creating exposure hazards because the syringe/needle assembly does not adequately fit into the sharps container.
In light of at least the foregoing, a need exists for a safety needle assembly that is constructed to provide desirable safety characteristics while also being constructed to facilitate usage by the user.